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5/09/2012 @ 12:35PM2,897 views

How Much Gas Has Total's Elgin Well Leaked So Far?

(Important update and correction May 9: as a more mathematically gifted reader has pointed out, my initial calculations overstated significantly the carbon dioxide equivalent of the methane that has so far leaked out of the well. I have corrected the math below and crossed through my original numbers. Apologies to readers and to Total.)

(Update 2, May 10: Total in a release Thursday says that the rate of the leak has declined steadily from an estimated 200,000 cubic meters per day in late March, to 50,000 cubic meters per day now. A decline curve to this rate would likely mean that the cumulative gas leaked so far is less than half of the volume calculated below, or something on the order of 100 million to 150 million cubic feet. Applying this amount to the figuring below, the amount of carbon dioxide equivalents emitted is more like 60,000 tonnes, or the equivalent of the pollution that 10,000 cars would put into the air in a year. This mishap is looking less serious all the time.)

Since late March French oil giant Total has been working to quench a natural gas leak at its Elgin platform in the North Sea. Already Total has started drilling a relief well to intersect and kill the leaking well, while this week another drilling rig has arrived on scene to attempt to plug the well by pumping it full of heavy mud.

Unlike BP’s Macondo blowout in the Gulf of Mexico, nobody has died in this mishap, and the gas and condensates are leaking out of a valve assembly on the platform itself, not underwater.

There has been some spillage of condensates into the North Sea, but Total puts the total volume at less than 100 barrels. Because the condensates are light and volatile (like propane or gasoline) they’ve mostly evaporated.

The leaking gas is a different story. Total has said that the amount of gas escaping the well into the air is was initially estimated at 200,000 cubic meters a day. Is that a lot? Let’s do the math and find out.

A cubic meter is about 35 cubic feet. So 200,000 cubic meters is 7 million cubic feet per day.

Is that a lot? Well, yes. It’s as good or better than the initial production rates of many wells drilled into U.S. shale formations like the Eagle Ford or Barnett or Marcellus.

Considering that the leak began about 45 days ago, on March 25, that’s roughly 300 million cubic feet of gas that has gone straight into the atmosphere. (The value of that gas? In the U.S. a thousand cubic feet sells for about $2.30, plus a premium for the condensates. The price of natgas in Europe is more than four times that. So Total has lost about $5 million worth of gas and condensates.)

Normally when big oil and gas fields have gas coming out that they can’t get into a pipeline they’ll ignite it and flare it off. Not only does this reduce the risk of accidental combustion, it is also the more environmentally friendly way of getting rid of the gas. The methane in natural gas is 24 times more potent as a greenhouse gas than is carbon dioxide.

Total obviously can’t flare the gas in this case because the entire platform would become a fireball and any hope they had of plugging the leak from above the water would disappear.

How big a deal is this methane leak in terms of air pollution? Well let’s convert it into the equivalent amount of carbon dioxide to get a better feel. According to the EPA’s handy conversion calculator, 300 million cubic feet of methane gas weighs 5.79 million metric tonnes kilograms. And because methane is 24 times worse than carbon dioxide as a greenhouse gas, those 5.79 million tonnes kilograms of methane equals 122 million tonnes kilograms of carbon dioxide.

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